Conventionally, for an image forming device, such as a copier and printer, there is known a technology which uses a special sheet set of a plurality of different kinds of special sheets that are disposed in a predetermined order, such as tab sheets having different tab positions or color sheets in a series of different colors, are disposed in a predetermined order, and performs printing while inserting special sheets at predetermined pages during printing. In performing printing by the use of such a special sheet set, it is required to perform printing while inserting right sheets at right positions.
In printing by the use of a special sheet set, if the quantity of special sheets used for printing one copy is not an integer multiple of the quantity of special sheets per set, unnecessary special sheet/sheets are left each time printing for one copy is completed. For example, using a tab sheet set of five tab sheets with respective different tabs, as shown in FIG. 9(a), and setting the insertion positions of tab sheets for each copy to be “front cover sheet/back cover sheet/after the second page”, when printing of one copy is performed, tab sheets up to the third tab are used. If printing is performed for the second copy following this, there is a problem that the tab sheet with the fourth tab is inserted as the front cover sheet, as shown in FIG. 9(b).
To solve such a problem, for example, in Patent Document 1, a technology is disclosed by which, in a case where the quantity of tabs used for one print copy is not an integer multiple of the quantity of tab positions, sheets with an unnecessary tab are ejected, not to be used, from a system so that printing for the next print copy is performed on right sheets.
Foe example, as shown in FIG. 10, in a case where a tab sheet set of five tab sheets with respective different tab positions and printing is performed in such a manner that the insertion positions of tab sheets in each copy are set as “front cover sheet/back cover sheet/after the second page”, after completion of printing for one copy, two unnecessary tab sheets which respectively have the fourth tab and the fifth tab are ejected, and thus tab sheets are correctly inserted also in printing the next copy.
[Patent Document 1] Patent No. 2728812
However, during performing printing by an image forming device, using a special sheet set, as described above, there have been a problem that a paper jam may occur and the order of special sheets is shifted in printing after releasing the jam. Further, also in a case where a jam occurs during ejection of special sheets, which have become unnecessary, there has been a problem that special sheets are ejected more than required for ejection, by which the order of special sheets is shifted.